Children's success in their primary social role as students is most effective when they are healthy and satisfied with their lives. Using a positive construction of health as a resource for participating and flourishing in major life activities, our research group has shown that over half of youth have a major health need. Poor health during middle childhood may interact with normative developmental demands to create a negative spiral of effects that interfere with engagement in school and adversely affect academic performance in early adolescence. This pattern is poorly understood, because little attention has been devoted to studying how health evolves between childhood and adolescence. We propose to test the hypothesis that positive health is necessary for successful school performance during the transition from middle childhood to early adolescence. We postulate that health comprises a set of resources that buffers individuals from endogenous and exogenous stressors and directly enhances the capacity to successfully participate in developmentally appropriate activities. This study has three specific aims: (1) to characterize longitudinal patterns of health among youth 9 to 13 years old; (2) to examine the longitudinal associations between health and biologic/individual factors (i.e. pubertal changes, demographics) and social environmental factors (i.e., life events, socio-economic status, and school transitions); and, (3) to assess how health experienced in middle childhood is related to school performance in early adolescence. We will enroll 2,000 students in grades 4, 5, and 6 attending schools in Maryland and West Virginia. Survey data will be collected from children, parents, and teachers at baseline, 12 months, and 24 months. School administrative records will provide data on school performance. Statistical analyses will model health trajectories and their relationship with school performance during the transition from childhood into adolescence. The proposed project bridges the conventional gaps between health and education, which are funded and administrated separately. This project builds on our team's decade-long experience developing health assessment questionnaires for youth. Findings from this work will inform the design of interventions that can close the school achievement gap among adolescents that results from their early health problems. Our long-term goal for this research is to follow youth into high school and beyond to more fully characterize the evolution of health from childhood to adulthood.